The present disclosure is related to wellbore operations and, more particularly, to fluid-based telemetry devices used in wellbore operations to selectively generate fluid pressure pulses.
In the oil and gas industry, drilling a wellbore, preparing the drilled wellbore for production, and subsequent intervention operations in the completed wellbore each involve the use of a wide range of different specialized equipment. For instance, a drilled wellbore is often lined with bore-lining tubing called “casing” that serves a number of functions, including sealing the wellbore and preventing collapse of the drilled rock formations penetrated by the wellbore. Generally, the casing comprises tubular pipe sections that are coupled together end to end to form a casing string. A series of concentric casing strings can extend from a wellhead to desired depths within the wellbore. Liner is a type of casing that comprises tubular pipe sections coupled end to end but does not extend back to the wellhead. Rather, liner is attached and otherwise sealed to the lower-most section of casing in the wellbore.
After the casing or liner is properly located within the wellbore, cement slurry is commonly pumped into the tubing and back out of the wellbore via the annulus defined between the tubing and the wellbore walls. Once the cement sets, the bore-lining tubing is secured within the wellbore for long-term operation.
A wide range of ancillary equipment is used in both running and locating casing within a wellbore. For example, measuring-while-drilling (MWD) tools are sometimes used to measure various wellbore parameters and guide casing strings to target locations within the wellbore. MWD tools are also able to communicate in real-time with a surface location, thereby providing real-time updates to a well operator of the wellbore parameters measured downhole and the current location and orientation of the casing string within the wellbore. Some MWD tools communicate with the surface location using mud-pulse telemetry, which consists of generating fluid pressure pulses that are transmitted to the surface through a column of fluid within the wellbore. Systems exist to generate ‘negative’ and ‘positive’ fluid pressure pulses that can be sensed and interpreted at the surface location.
In running casing into a wellbore, the MWD tool is often disposed in a probe positioned within the casing. This leads to inevitable wear and tear on the MWD tool, primarily through the processes of erosion as fluids circulate around and past the probe within the through bore of the casing. The cost of operating MWD equipment is therefore often determined by the required flow rates and types of fluids circulated within the wellbore. Furthermore, as the through bore of the casing is substantially obstructed by the MWD equipment and probe, it is difficult to pass other equipment through the through bore. For instance, actuating devices, such as hydraulic fracturing balls (“frac balls”) or other similar downhole equipment, are often conveyed downhole to actuate a sliding sleeve or valves. The MWD equipment and probe, however, may present a considerable obstacle in reaching the sliding sleeves or valves located below the MWD equipment.